Abstract
Cam-type femoroacetabular impingement (FAI) is a common cause for athletic hip injury and early hip osteoarthritis. Although corrective cam FAI surgery can improve patient reported outcome measures (PROMs), it is not clear how surgery affects muscle forces and hip joint loading. Surgery for FAI may redistribute muscle forces and contact forces at the hip joint during routine activities. The purpose of this study was to examine the muscle contributions and hip contact forces during gait in patients prior and after two years of undergoing surgery for cam FAI. Kinematics and kinetics were recorded in 11 patients with symptomatic cam FAI as they completed a gait task. Muscle and hip contact forces during the stance phase were estimated using musculoskeletal modelling and static optimization in OpenSim. All patients reported improvements in PROMs. Post-operatively, patients showed reduced forces in the long head of the biceps femoris at ipsilateral foot-strike and in the rectus femoris at the contralateral foot-strike. The reduced muscle forces decreased sagittal hip moment but did not change hip contact forces. This was the first study to evaluate hip muscle and contact forces in FAI patients post-operatively. Although hip contact forces are not altered following surgery, muscle forces are decreased even after two years. These findings can provide guidance in optimizing recovery protocols after FAI surgery to improve hip flexor and extensor muscle forces.
